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I guess it may due to variable cache. if php script use apc_delete(), then it may cause fragment illustrated in the screenshot. to experiment, you can temporarily disable variable cache to watch the fragment status.

I guess it may due to variable cache. if php script use apc_delete(), then it may cause fragment illustrated in the screenshot. to experiment, you can temporarily disable variable cache to watch the fragment status.

Click to expand...

How to temporarily disable variable cache?

However since first post, i've doubled shm size (6gb now), and fragmentation is still ugly.

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did some search, have not found a simple way to disable user variable cache.

for fragment, it's more relating to add/delete cache entry frequently.
since you set
apc.ttl 0
apc.user_ttl 7200
which add operation can be 0 if shared memory always have free space(in your case). but if php script use apc_delete() to delete cache entry purposely, it will cause fragment.

did some search, have not found a simple way to disable user variable cache.

for fragment, it's more relating to add/delete cache entry frequently.
since you set
apc.ttl 0
apc.user_ttl 7200
which add operation can be 0 if shared memory always have free space(in your case). but if php script use apc_delete() to delete cache entry purposely, it will cause fragment.

Click to expand...

My site has guests & logged in visitors. For guests, the view is cached entirely by APC (i think) to speedup site. Considering the amount of guests and cached pages, i agree maybe add operation is frequent. But apc_delete is not used frequently on my site i believe, because i set the script to cache on long time (5 hours).